System Description [08/2019 - ]
- BRIEF DESCRIPTION
- The Controller Area Network (CAN) is a serial data communication system for real time application. It is a vehicle multiplex communication system which has a high communication speed and the ability to detect malfunctions.
- Using the CANH and CANL bus lines as a pair, CAN communication is performed using a voltage differential. (A base voltage is applied to the pair of lines and a voltage differential is created when communicating.)
- Many ECUs or sensors installed to the vehicle operate by sharing information and communicating with each other.
- 2 resistors which are necessary for communication are used in a CAN bus main line.
- DEFINITION OF TERMS
- Central bus
- The central bus is a generic name for multiple subordinate CAN bus lines on the central gateway ECU (network gateway ECU).
HINT:
A bus is displayed as Bus on the "Communication Bus Check" screen of the Techstream.
- The central bus is a generic name for multiple subordinate CAN bus lines on the central gateway ECU (network gateway ECU).
- Sub bus
- A sub bus is a bus that has a gateway function equipped ECU in order to communicate with the central bus and other sub buses.
HINT:
- A sub bus is displayed as Sub bus on the "Communication Bus Check" screen of the Techstream.
- When Sub bus is selected on the "Communication Bus Check" screen, ECUs and sensors connected to non-CAN networks such as LIN may also be displayed in addition to the ECUs and sensors connected to sub buses in the CAN network.
- A sub bus is a bus that has a gateway function equipped ECU in order to communicate with the central bus and other sub buses.
- Local bus
- A local bus is a bus that does not have the ability to communicate with other buses. ECUs and sensors on a local bus can only communicate with other ECUs and sensors on the same bus.NOTE:
Gateway function not equipped ECU is a generic name for ECUs not connected to the central gateway ECU (network gateway ECU) with a gateway function.
- A local bus is a bus that does not have the ability to communicate with other buses. ECUs and sensors on a local bus can only communicate with other ECUs and sensors on the same bus.
- CAN J/C
- A CAN junction connector is a connector that connects branch lines to a main bus.
- Main bus
- A main bus line is the wire harness that runs between the 2 terminating resistors of a bus.
- Branch
- A branch line is a wire harness that connects an ECU or sensor to a main bus line.
- Terminating resistors
- Terminating resistors which maintain a stable signal inside the CAN bus are installed. 2 resistors of 120 Ω each located at each end of the bus are necessary.
- except Diagnosis Bus:
2 resistors of 120 Ω each located at each end of the bus are necessary.
- for Diagnosis Bus:
1 resistor of 60 Ω located at end of the bus are necessary.
- except Diagnosis Bus:
- Terminating resistors which maintain a stable signal inside the CAN bus are installed. 2 resistors of 120 Ω each located at each end of the bus are necessary.
- Central bus